Free flowing resin particles are particularly useful in injection molding apparatus which employ a hopper to feed an extruder. While some mechanical agitation can be employed, the resin particles generally fall into a heating zone by gravity. Many patents exist which disclose free flowing resin or polymer particles as well as processes for making the same. One of these is U.S. Pat. No. 3,769,256 which is directed toward an unvulcanized rubber composition comprising a styrene-butadiene copolymer and from about 5 to 200 parts of hydrous silica. The composition possesses a high tensile strength prior to vulcanization and is processable by conventional methods including injection molding, extruding and the like. In order to provide the increase in unvulcanized tensile strength, the patent teaches hydrogenation of the copolymer, styrene-butadiene, and the addition of fillers.
U.S. Pat. Nos. 3,998,778 and 4,073,755 provide respectively for finely divided, powdered elastomers such as polybutadiene and the process for preparing the same. The particles are the result of solution polymerization of butadiene which is thereafter emulsified. An aqueous suspension of carbon black is added followed by an aqueous sodium silicate solution. The examples disclosed report the use of polybutadiene solutions having a vinyl content of only about 35 percent, the disclosed range being only 15 to 75 percent. Powdered particles, although free flowing, are not always desirable inasmuch as they provide quantities of dust effecting waste of material as well as pollution problems.
Thus, none of the patent literature known to us provides a high vinyl, high molecular weight polybutadiene resin in a granular free flowing form. Nor, is a process disclosed wherein a free flowing nature can be imparted to the polymer.